Abstract

Isotope shifts for various lines associated with excitations of transition-metal impurities in semiconductors are considered. Special attention is paid to $\mathrm{Z}\mathrm{n}\mathrm{O}:\mathrm{C}\mathrm{u},$ for which experimental results are presented. Isotope shifts are measured for the so-called photoluminescence $\ensuremath{\alpha}$ and $\ensuremath{\beta}$ zero-phonon lines associated with excitations of bound excitons, and of the zero-phonon line associated with the intracenter ${\mathrm{Cu}}^{2+}{(}^{2}{T}_{2}{\ensuremath{-}}^{2}E)$ transition. These shifts appear to be negative and nearly equal. A theoretical model explaining these results is proposed, which incorporates the mode softening mechanism and the covalent swelling of the impurity $d$ electron wave functions. It is shown that, contrary to transitions in simple neutral impurities, this mechanism works both for the excited and ground states of all processes in transition-metal impurities considered here. Using reasonable values of the parameters of the system, we are able to explain both the sign and value of the isotope shifts.

Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call